This invention relates to a coupling arrangement between the horizontal and vertical deflection system useful in a television receiver.
A switched synchronous vertical deflection system is described in U.S. Pat. No. 4,048,544, issued Sept. 13, 1977 to Peter Eduard Haferl and entitled "SWITCHED VERTICAL DEFLECTION SYSTEM". In this arrangement, the energy for the vertical deflection system is derived from the horizontal deflection system by means of switched reactances. The switched reactances are coupled to the horizontal deflection generator by means of a transformer, a primary of which is connected to the horizontal deflection generator and at least one secondary of which is connected to the switched reactances. In the aforementioned arrangement of U.S. patent application Ser. No. 595,809, a further secondary winding of the transformer is a high voltage winding from which the kinescope ultor voltage is derived by rectification.
When video is displayed on the kinescope of the television receiver, beam current variations cause a varying load on the secondary winding from which the ultor voltage is derived. These variations in turn cause variations in the magnetic flux in the core of the transformer dependent upon the kinescope beam current. The changes in magnetic flux in the transformer in dependence upon the video content of the information being displayed by the kinescope in turn changes the incremental transformer mutual inductance, due to the nonlinearity of the relationship between magnetizing force and flux in the core. This may result in undesired variations in the coupling of energy between the horizontal deflection generator and the vertical deflection generator with resulting imperfect vertical linearity.